In shipping a package, it often requires a proper temperature control of the object being packed and shipped. For example, frozen food samples are shipped from the present inventor""s food manufacturing plant to our customers on a daily basis. These frozen samples require a good control of their packaged temperature in order to keep them frozen and fresh. The packaged temperature can be controlled externally using a refrigerated environment such as the refrigerated compartment of a xe2x80x9crefer-truckxe2x80x9d. However, for a relatively small size shipment of samples, or other refrigerated products, for convenience and for economical reasons, we often ship the products through a common carrier without refrigeration facilities. A common method of shipping such product through a common carrier is to use a cold substance such as xe2x80x9cdried icexe2x80x9d (solid carbon dioxide) to help maintain a frozen product temperature in addition to using a good insulator around the product along with the xe2x80x9cdried icexe2x80x9d.
The present invention involves (i) a new insulating package providing good insulation for a product using an ordinary insulating material without the need for using additional cold substances such as the xe2x80x9cdried icexe2x80x9d mentioned above, and (ii) a device to prepare such a new package mentioned in (i). The present invention can also be used in conjunction with any other conventional packaging methods such as the one using the xe2x80x9cdried icexe2x80x9d, to enhance the result of maintaining the product temperature.
Generally speaking, heat is transferring from one object to another by one or more of the three well-known mechanisms, namely (i) conduction through a solid medium, (ii) radiation through space and (iii) convection through a fluid medium. Strictly speaking, convection and conduction are in the same heat transfer category. But conduction involves only a solid medium, while convection involves heat transfer through the xe2x80x9cboundary layerxe2x80x9d of a fluid medium at the vicinity of a solid, and is greatly affected by the xe2x80x9cfree stream velocityxe2x80x9d of the medium. In convection, the xe2x80x9cfilm coefficient of heat transferxe2x80x9d which is a function of the xe2x80x9cfree stream velocityxe2x80x9d, is used as the indicator of the transferability of conductive heat from a solid to a fluid or vice versa. The above mentioned transferability is zero in the absence of a fluid medium, namely in a vacuum. The xe2x80x9cfilm coefficient of heat transferxe2x80x9d is equivalent to the xe2x80x9cheat conductivityxe2x80x9d in conduction. Heat radiation, however, is a different physical phenomenon involving the transferring of microscopic particles and wave from an object to another through space with or without a medium. In a macroscopic investigation of heat radiation, each object has its heat emission, absorption and reflection characteristics. The absorption and reflection characteristics, however, are strictly related to each other. The difference in the total emission and absorption between two given objects results in the net radiation heat transfer from one object to the other.
All three categories of heat transfer mentioned above have been taken into consideration in the present invention so that the overall heat transfer from outside the package to the packaged product or vice versa is minimized.
The temperature enclosed package, in one embodiment, has a reflector surrounding the product, a frame with a cavity placed around the reflector, an insulating enclosure placed around the frame, and a diaphragm placed around the insulating enclosure. A vacuum is produced within the temperature controlled package.